I was surprised to learn that the Common house gecko, Hemidactylys frenatus, has expanded its native SE Asian range to include some Pacific Islands, Australia, South Africa, the southern USA and so on. It has even invaded Texas! I wonder how they move around?
Flying lizards are a common group of agamids in southeast Asia. The Common Gliding Lizard, Draco Volans – also called the Javanese flying lizard – is found in Java and Bali (1). These photographs were taken in Bali Barat NP, so perhaps they should be called the Balinese flying lizard. The males have a very obvious, pointed yellow gular flag, which they constantly flick up and down to signal to other members of their species.
Spend a few minutes watching these lizards and they reveal a variety of different behaviours, including: push-ups (head bobbing), ﬂattening themselves against the trunk of the tree, extending their peculiar throat (or gular) flap, raising their tail and so on. They are incredible fast-moving and energetic when they want to be and I got the impression that there was a constant buzz of activity going on, with males chasing females and challenging other males for territory. What is really incredible is when they launch themselves into the air and fly – gliding really – from tree to tree. It is quite startling if you have never seen it before. I couldn’t believe how adept they were at gliding through the forest. Unfortunately I did not manage to get a photograph of them flying. They are able to glide considerable distances, say 30m or so, by extending the expanding the loose skin – called the patagium – on the sides of the body. This ‘wing’ is usually folded away and can only be guessed at by the tightly folded skin on the sides of their body (below).
Lizards of many different species perform push-up movements and head-bobbing. Three different types of push-ups were recorded for the Sumatran subspecies, Draco volans sumatranus! (2) Quite what all these signals mean is only fully known to the lizards themselves, but probably has to do with communicating the attributes, size, status and so on, of the lizard carrying out the display. Some movements, like the so-called, dorsal flattening, is carried out when birds fly past overhead, and simply serves to improve the already excellent camouflage (see below).
They are said to mostly feed on ants, so serve a very useful ecological function.
The females have a small, mottled, bluish gular flag but I did not witness one waving it! All that can be seen on the females in these photographs is a blueish throat. Females of some species of lizard raise their tails in response to encountering a male (3); so perhaps this one (below) was doing just that?
It would be fascinating to watch and study the behaviour of these lizards in more detail. There is a repertoire of behaviours going on; I am sure that there is much to be discovered.
- Mori, A., & Hikida, T. (1994). Field observations on the social behavior of the flying lizard, Draco volans sumatranus, in Borneo. Copeia, 124-130.
Radder, R. S., Saidapur, S. K., Shine, R., & Shanbhag, B. A. (2006). The language of lizards: interpreting the function of visual displays of the Indian rock lizard, Psammophilus dorsalis (Agamidae). Journal of ethology, 24(3), 275-283.
There’s not an awful lot to say about Komodo dragons, other than the fact that they are a huge lizard – the biggest in the world – and give us an indication of the reptilian megafauna that once stalked the earth.
They are not creatures I think anyone could find attractive. Respect, admiration and awe, but not affection. They are just too reptilian, too unknowable. What is going on in that tiny brain when it looks at us. Just the notion, I think, that we are edible!
I didn’t really like them, with their deer-chomping habits and slimy mouths, but they are magnificent animals and I am very glad to have had the opportunity to see them up close.
I must confess that they did have an air of dignity about them. When this large one approached the water hole to drink, we scattered, but he remained still, upright and alert (first photo) for some time before moving in for a drink. After all it was his water hole. Was he being cautious or dignified? Maybe a bit of both. He (or she) had probably been drinking there for decades whilst we were only spending a fleeting hour on the island.
The ones on the beach were said to have been fed occasionally, which is why they are very interested and attentive when zodiacs containing tourists arrive to gawp at them and take pictures.
The young ones, which spend most of their lives up trees to avoid being eaten by the larger ones, are almost cute. Until I saw one catch, kill and swallow a rat (below sequence).
It stalked it up a tree and then fell to the earth with a thud. It then raced off to a quiet spot (not so quiet on account of the photographers following it with their cameras!) and proceeded to swallow it whole. They shan’t be on my Christmas list. But like them or loath them, they deserve respect; for surviving so long if nothing else!
The poor animals which God, sorry evolution, has elected to be food for these giant lizards, are an attractive cervid called the Timor deer. It must be a rum existence never knowing when one of these lizards is going to inflict a venomous bite leaving you hobbling around waiting to be eaten. But perhaps only the weak and sickly get taken. This deer did not seem at all concerned about the presence of the dragons nearby.
All photographs taken in Komodo National Park in October 2016.
I am very fond of skinks and it was a pleasure to see this beautiful creature on a number of occasions in Bali recently. They are however, rather shy and I only managed to get some decent photographs in one location: the Bali Mangrove forest walk. These lizards are kept as pets by some people, so it is not hard to understand why wild ones are a little leery of human beings. These lizards have also been moved around S E Asia by humans in the past, either knowingly or unwittingly in goods and transport.
The Many-lined Sun skink, Eutropis multifasciata – which was formerly known as Mabuya multifasciata – is a medium-sized, lizard, which gives birth to live young (vivipary). There can be between two to seven baby skinks in a litter (1). The Many-lined sun skink has a very wide tropical distribution, ranging from southern China west to India, south to Malaysia, Singapore, Indonesia, the Philippines, and New Guinea (2). Here is a picture of one I took in Chiang Dao, in northern Thailand (below).
The name ‘many lined’ refers to the dark scale lines (five to seven) which run longitudinally down the dorsal (back) side of the body. The Balinese skink clearly has the same pattern, as can be seen in the following photograph of one climbing up a curb to a path in the Bali Mangrove Forest (Mangrove Forest Nusa Lembonga).
The Many-lined Sun skink is a variable species and the colour of the flanks can vary from olive-brown to reddish-orange (3). The throat colour is also reportedly variable, from white to yellow (3). These skinks have the endearing habit of lifting one or two limbs off the ground, presumably to cool down. The same skink has raised its left hind-limb in the above photograph, but a few moments later raised its left fore-limb for a few seconds on top of the wall (below).
Sun skinks feed on invertebrates such as spiders, insect larvae, snails, grasshoppers and crickets (4). I’m not sure if this one was a male or female, but males are slightly larger than females and have larger heads. The Bali skink is very characteristic with its lovely yellow scales running along its flank. Other varieties of this species have a more orange colour, but all the ones I saw on Bali were yellow.
It’s tempting to think that something that looks so different is a different species, but that is not always the case if varieties can interbreed. Populations on islands such as Bali have become genetically isolated and are reportedly somewhat different from mainland populations, but not by very much. Examples of the different varieties are shown on Link 3. The Balinese skink was first named as a separate subspecies by a German herpetologist called Robert Mertens in about 1930 (5).
Despite the rather obvious differences between some varieties of this widespread species, recent research suggests that the Bali skink is not sufficiently different to qualify as a separate subspecies. For example, it was only about 1% different in terms of its mitochondrial RNA, from E. multifasciata populations on nearby Java (6). Presumably they could interbreed, but perhaps this has never been tested! It’s a pity that it is not a separate subspecies in a way, as the Bali skink looks so different, but the yellow coloured scales on the flanks is probably a superficial character and may not amount too much. That said, I bet the skinks know which ones come from Bali and which ones come from other islands!
The Bali skinks were further inland from the actual mangroves where another skink – Mangrove Skink (Emoia atrocostata) – was very abundant.
Links and references
- Sexual dimorphism and female reproduction in the many-lined sun skink (Mabuya multifasciata) from China. Journal of Herpetology, 40(3), 351-357.
- SUN, Y., Yang, J., & Ji, X. (2009). Do not Compensate for the Costs of Tail Loss by Increasing Feeding Rate or Digestive Efficiency. JOURNAL OF EXPERIMENTAL ZOOLOGY, 311, 125-133.
- Ngo, C. D., Ngo, B. V., Truong, P. B., & Duong, L. D. (2014). Sexual size dimorphism and feeding ecology of Eutropis multifasciata (Reptilia: Squamata: Scincidae) in the Central Highlands of Vietnam. Herpetol Conserv Biol, 9, 322-333.
- Mertens, R. (1930): Die Amphibien und Reptilien der Inseln
Bali, Lombok, Sumbawa und Flores. Abh. Senckenberg.
Naturf. Gesell. 42: 115–344.
- Mausfeld, P., & Schmitz, A. (2003). Molecular phylogeography, intraspecific variation and speciation of the Asian scincid lizard genus Eutropis Fitzinger, 1843 (Squamata: Reptilia: Scincidae): taxonomic and biogeographic implications. Organisms diversity & evolution, 3(3), 161-171.
Bocage’s Wall Lizard (Podarcis bocagei) is only found in the NW corner of the Iberian Peninsula, including Galicia, Spain. It is a small lizard which is often seen on wooden broad-walks, where it pops up to bask in the sunshine. They quickly disappear beneath the planks when heavy footed humans get near!
The sexes are differently coloured: the mature males have a green upper (dorsal) surface, whilst the females have a brown one, usually! As well as a green back, the males also have brown flanks (as shown below). These little lizards only live for about four years. The males quickly turn green once they have reached sexual maturity, and have only 2-3 years as an adult (1).
Many animals, from butterflies to lizards, are faced with conflicting demands in terms of their biology. Whilst they need to remain hidden – inconspicuous and cryptically coloured – to avoid predation, they also need to be bright and conspicuous in order to signal their sexual prowess, or fitness. Males are usually, but not always, the sex which signals their overall genetic fitness in terms of bright colouration and showy displays. The females choose who they want to mate with, based on these colours or displays.
I took this photo (top and below) of a nice bright green male Bocage’s Wall Lizard (Podarcis bocagei) in May, this year. The breeding season runs from April to July. He let me get quite close; I guess he didn’t want to move out of this warm, sunny spot unless he had to!
Breeding males also turn a bright yellow colour on their under (ventral) sides, during the reproductive period. Unfortunately, I was not quick enough to catch this one and turn it over! It is difficult enough to get sufficiently close to get a good photograph.
Somewhat confusingly, a small proportion (less than 10%) of female lizards of this species turn green after mating, particularly in coastal areas (2). I blogged about this phenomenon previously (3). So it’s possible he is a she! And it does look quite fat, as though it was gravid (pregnant). Some things we will never know!
Photographs taken near Morouzos beach, Ortigueira, Galicia, Spain.
- Galán, P. (2008). Ontogenetic and sexual variation in the coloration of the lacertid lizards Iberolacerta monticola and Podarcis bocagei. Do the females prefer the greener males?. Animal Biology, 58(2), 173-198.
- Galán, P. (2000). Females that imitate males: dorsal coloration varies with reproductive stage in female Podarcis bocagei (Lacertidae). Copeia, 2000(3), 819-825.
I came across quite a few tegus – large lizards – when visiting Iguazu National Park in northern Argentina. As far as I can tell, they are all the Argentine black and white tegu (Salvator merianae), also called the Argentine giant tegu (1). They wander round quite happily, despite the presence of large numbers of people coming to see the waterfalls.
Tegus seem to eat just about everything! That is why are called omnivores: omni means ‘all’ or ‘every’. They will apparently consume invertebrates (millipedes, arachnids, insects and molluscs), vertebrates (birds, fishes, amphibians, lizards and small mammals), bird and turtle eggs, fruits, carrion and mushrooms (2). It’s not surprising given this diet that they grow so large! Over four feet long.
Tegus look a lot like monitor lizards (an Old World group) but they are not closely related, so must be assumed to have evolved to fill a similar niche (convergent evolution). There are 7 species of tegus, which were originally placed in a single genus, Tupinambis. But tegu taxonomy seems to have gone through some changes recently and the Argentine black and white, or giant tegu, was recently reclassified as Salvator merianae (3). For the record, the genus Salvator now consists of three species: S. duseni (The Yellow tegu), S. merianae and S. rufescens (The Red tegu), which mainly occur in open ecosystems (4). The genus Tupinambis now contains four species: T. longilineus (The Rondonia tegu), T. palustris (The Swamp tegu), T. quadrilineatus (The Striped or Four-lined tegu) and T. teguixin (The Golden tegu); and these tegus are mainly to be found in forest ecosystems (4).
Some of the tegus I photographed, like the individuals shown above and below, had a more yellow or golden colour and I wondered if these could have been Golden tegus (Tupinambis teguixin). Tegus are separated on the basis of a large number of characters, one of which is the number of loreal scales they have (3, 4). These are the large scales between the eyes and nostrils. All of the individuals shown here seem to have two large scales, so they cannot be T. teguixin, as that species only has one large loreal scale (4).
Surprisingly, tegus make good pets! Apparently, they are quite docile and can be house trained; they also get quite attached to their owners and get aggressive if they are not handled regularly! (1, 2). There are a number of Facebook sites (e.g. ‘The Tegu-phile’ and ‘Tegus from Around the World’) for people who love tegus! Unfortunately, not everyone appreciates their good nature and many are hunted for food and skins (5). Despite this fact, their numbers seem to be holding up.
There were also some very nice waterfalls as well as lizards!
- Harvey, M.B., G.N. Ugueto and R.L. Gutberlet Jr. 2012. Review of Teiid Morphology with a Revised Taxonomy and Phylogeny of the Teiidae (Lepidosauria: Squamata). Zootaxa 3459: 1-156.
- Passos, D. C., Lima-Araujo, F., Melo, A. C. B., & Borges-Nojosa, D. M. (2013). New state record and distribution extension of the golden tegu Tupinambis teguixin (Linnaeus, 1758)(Squamata: Teiidae) to the Caatinga biome, northeastern Brazil. Check List, 9(6), 1524-1526.
- Embert, D., Fitzgerald, L. & Waldez, F. 2010. Salvator merianae. The IUCN Red List of Threatened Species 2010:e.T178340A7526681. http://www.iucnredlist.org/details/178340/0
The Southeast Asian water monitor, a large lizard called Varanus salvator subspecies macromaculatus, occurs throughout southern Asia and Southeast Asia. It can grow very large, apparently up to 3 m in length, although most adults are about 1.5 to 2 m long (1). Big enough! The males are larger than the females and can weigh up to 50 kg. Their big cousins, the Indonesian Komodo dragons (Varanus komodoensis), are of course much larger and weigh up to 150 kg. Anyway, these Bangkok dragons are impressive enough.
The water monitors have adapted well to life in Bangkok – I expect they have been there throughout the history of the city – and can be seen in many places, including klongs and canals; most prominently in Lumpini Park.
Lumpini (or Lumphini or Lumpinee) – สวนลุมพินี in Thai – is a 142 acre haven of peace in the centre of Bangkok. It is a place were it is possible to see a surprising number of birds and other animals, including these amazing reptiles which have become used to people (albeit with a degree of wariness on both sides).
The water monitors are said to do a useful job of helping to keep the city clean, by feeding on edible rubbish and so on and controlling insects, snails and rodents (2). They are predators as well as scavengers.
Their natural habitat is a burrow in a river bank, so the water culverts which open out onto the artificial lakes in the park provide them with ready-made homes. They can be seen swimming in and out of these concrete tubular openings.
Asian water monitors are excellent swimmers and have been seen swimming between islands in southern Thailand (3). So the lakes in the park provide no challenge and they can be seen swimming alongside some of the pleasure boats, much to the amusement of tourists.
I expect they also take a number of other species which are found in the park, especially frogs, birds (eggs) and even turtles. Although, perhaps it’s even-stevens, as herons and egrets will eat baby monitor lizards if they get a chance. It all seems to work out.
There is a picture of a water monitor trying to swallow a fairly large turtle on the Internet! Fortunately, this Yellow headed temple turtle which was resting on the shore of the lake in Lumpini Park was much to large to get eaten!
There are also lots of cats of all shapes and sizes living in Lumpini Park, but I expect they are far too smart to get caught and eaten by a lizard, however big it might be!
But monitor lizards are no slouches. According to one expert, they ‘can count, have memories, have shown map knowledge, and plan ahead’ (4). That’s more than some people I know!
They can look quite scary, especially when they flick out their forked tongue, tasting the air!
In Indonesia they are turned into shoes and handbags! There is reportedly a reptile leather industry which exports ~40,000 skins from that country (1). According to one report, over 20 million monitor lizards were killed for their skins between 1995 and 2005 (4). They are also eaten for food, although they are a protected species in Thailand (2). I don’t think I would like to eat one from the sewers, but it would probably depend how hungry I was!
Anyway, I always enjoy seeing animals that have adapted well to Man’s environment, and these creatures appear to be thriving in the parks and canals of BK. It is perhaps no coincidence they do so well as Thailand is a Buddhist country and respects wildlife, even though these lizards are supposedly a symbol of bad luck. Maybe that is why they are left alone. They have been on this planet for an awful lot longer than us, so let’s throw them a bit of respect.
- BORDEN, R. 2007. Varanus salvator (Asian Water Monitor) Migration. Biawak 1 (2): 84
- Pianka, Eric R. 2012. Can humans share spaceship earth? Amphibian & Reptile Conservation 6 (1): 1-24
Pholidosis is a name used by zoologists to refer to the pattern or arrangement of scales on the bodies of animals such as reptiles. The pattern of scales on different parts of the body can be used by zoologists to separate closely related species. For example, ‘pholidotic patterns’ were used to separate two closely related lizards (Podarcis bocagei and Podarcis carbonelli), which are only found in the western Iberian Peninsula (1, 2). One of them is shown here, in close up.
I wrote a blog about this little lizard before (3), but I did not know that there was a very similar species in Portugal, just to the south of Galicia, called Carbonell’s wall lizard (4). The two species are separated by a river (the Duoro), a climatic barrier which also marks the boundary between Portugal and Spain for much of its length (2). So here we have two lizards, separated by geography, nationality and scales!
Kaliontzopoulou, Antigoni, Miguel A. Carretero, and Gustavo A. Llorente. “Differences in the pholidotic patterns of Podarcis bocagei and P. carbonelli and their implications for species determination.” Revista Española de Herpetología19 (2005): 71-86. http://lacerta.de/AS/Bibliografie/BIB_1387.pdf
Sá-Sousa, Paulo. “Comparative chorology between Podarcis bocagei and P. carbonellae (Sauria: Lacertidae) in Portugal.” Revista Española de Herpetología15 (2001): 85-97. http://lacertilia.de/AS/Bibliografie/BIB_1375.pdf
I came across this lizard enjoying the late afternoon sunshine at the back of the Mirador da Miranda viewing point, which is a stone balcony overlooking the Ria Ortigueira and surrounding countryside in Galicia, Spain. The lookout point must be about 500m in altitude and overlooks the Ria (or inlet) (see below).
Iberian mountain lizards (L. (I.)monticola) have a fragmented distribution, with two subspecies, separately located in 1) the Serra da Estrela mountains of Central Portugal [I. monticola monticola] and 2) NW Spain [I. m. cantabrica] (1, 2). The subspecies shown here – Iberolacerta monticola cantabrica to give it its full name – occurs in a continuous distribution from Galicia in the west, all the way along the Cantabrian Mountain Range to the Picos de Europa, in the east. This lizard like mountains, and is mostly found in rocky places between 700 and 1,000m above sea level; but in Galicia for some reason, it occurs down to sea level.
The two subspecies probably became separated from each other – and evolved differences – during past ice ages, when they occupied so-called glacial refugia (3). The Iberian Mountain lizard is defined as ‘‘vulnerable’’ in the IUCN Red List of Threatened Species, because its limited distribution is severely fragmented, and the quality and extent of its existing habitat is continuing to decline (3). So it was nice to see this plump female warming herself in the sun, perhaps getting ready to lay a clutch of eggs? It’s a shame I did not see the male, which is an attractive bright green colour, with black spots.
1. Arribas, Oscar, Salvador Carranza, and Gaetano Odierna. “Description of a new endemic species of mountain lizard from Northwestern Spain: Iberolacerta galani sp. nov.(Squamata: Lacertidae).” Zootaxa 1240 (2006): 1-55.
2, Almeida, A. P., et al. Genetic differentiation of populations of Iberian rock‐lizards Iberolacerta (Iberolacerta) sensuArribas (1999). Journal of Zoological Systematics and Evolutionary Research 40.2 (2002): 57-64.
3. Remón, Nuria, et al. “Causes and evolutionary consequences of population subdivision of an Iberian mountain lizard, Iberolacerta monticola.” PloS one 8.6 (2013): e66034.